A film formed of densely packed amorphous carbon nanofibers is synthesized by chemical vapor deposition using acetylene and hydrogen gases as precursors and copper nanoparticles (<25 nm in diameter) as the catalyst at low temperatures (220-300 °C). This film has a high concentration of sp3 carbon (sp3/sp2 carbon ratio of ∼1-1.9) with a hydrogen concentration of 25-44 atom %, which qualifies it as hydrogenated diamond-like carbon. This hydrogenated diamond-like carbon nanofiber film has properties akin to those of diamond-like carbon films. It has a high electrical resistivity (1.2 ± 0.1 × 106 Ω cm), a density of 2.5 ± 0.2 g cm-3, and is chemically inert. Because of its morphology, different from diamond-like carbon films on the nanometer scale, it has a higher surface area of 28 ± 0.7 m2 g-1 and has differences in mechanical properties, such as Young's modulus, hardness, and coefficient of friction. The hydrophobicity of this film is comparable to the best diamond-like carbon films, and it is wettable by oil and organic solvents. The nanofibers can also be separated from the substrate and each other and be used in a powder form.
Keywords: amorphous carbon nanofiber; buckling; carbon film; diamond-like carbon; sp3/sp2 carbon ratio.